Yes.
The braking system is still hydraulic, with the typical dual master cylinder driving conventional disc brakes.
However, the booster is now electric. Tesla appears to be using a version of Bosch's iBooster system - there is an electric motor geared directly to the master cylinder piston, which can apply boost (or apply the brakes without the operator) at any time, using electric power to pressurize the hydraulic fluid in the brake system.
Walter